I agree about the Boerbull and find they are a one man dog and are not very social with smaller dogs. I have owned English mastiff with small dogs aswell as Bullmastiffs. I found the bullmastiff to be the one which would tend to leave the small dog alone and play occasionally but was very gentle. I had a dashhound and Jack Russell which got on fine with her. So in my experience I would go with the Bullmastiff.